Known as a conventional laser processing apparatus is one which converges first and second laser light having wavelengths different from each other at an object to be processed, so as to cut the object. For example, the following Patent Literature 1 discloses a laser processing apparatus which ablates a portion of a substrate by using a first radiation pulse of a first ultraviolet wavelength and a second radiation pulse of a second ultraviolet wavelength longer than the first ultraviolet wavelength. For example, the following Patent Literature 2 discloses a laser processing apparatus which cuts an object to be processed by using an oscillated wave of laser light and its harmonic.
On the other hand, a laser processing apparatus has recently been developed, which converges pulsed laser light at an object to be processed, so as to form a plurality of modified spots within the object along a line to cut and cause the plurality of modified spots to produce a modified region as disclosed in the following Patent Literature 3, for example.